1. Field of the Invention
The present invention relates to an acceleration sensor, for example, which is built in a gas or other flow meter so as to shut off a valve of a gas pipe or in a stove so as to extinguish flame when detecting earthquake vibrations and the like, or which detects accelerations in many directions on a two-dimensional plane at approximately the same sensitivity.
2. Related Arts
JP-A-6-123631 and JP-A-6-123632 disclose a semiconductor acceleration sensor capable of being used for the above field. The semiconductor acceleration sensor has an anchor part supported by four beams such that it can move in X, Y directions and a movable electrode which moves together with the anchor part. This sensor detects accelerations in the X, Y directions based on a change in capacity between the movable electrode and a fixed electrode provided on a substrate side, so that it detects acceleration in every direction on an X-Y plane.
However, to obtain the magnitude of acceleration in a diagonal direction on the X-Y plane based on the detected accelerations in the X, Y directions, it is necessary that the acceleration sensor has an arithmetic circuit for synthesizing the detected accelerations in the X, Y directions to process as a signal.